Exploring Wetting Dynamics on Superhydrophobic Nanopatterned Surfaces Using ATR-FTIR

Abstract

Accurate characterization of the underwater stability of superhydrophobic surfaces is crucial for the design of durable anti-fouling materials and advanced microfluidic concepts. Although superhydrophobic breakdown is a major issue that hampers full exploitation of superhydrophobic functional materials, suitable characterization methods are lacking and relatively little is known about the wetting dynamics. In this work we explore a novel method based on attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) for large-area in-situ analysis of wetting states and wetting transitions on nanostructured surfaces. Spontaneous wetting is induced on superhydrophobic silicon nanopillars through in-situ modulation of the liquid composition and surface tension. The high surface sensitivity of ATR-FTIR enables quantitative evaluation of the instantaneous liquid composition and wetted area. Critical transition criteria for superhydrophobic breakdown are assessed using both ATR-FTIR and goniometric measurements. Significant deviations from classical wetting models are revealed, emphasizing the need for more accurate transition criteria and careful experimental validation. Breakdown kinetics near the critical transition are found to be significantly slowed down on nanostructured surfaces, which underlines the necessity for accurate characterization of wetting dynamics at the nanoscale. The proposed ATR-FTIR method can be promising for dynamic studies of wetting transitions on more advanced surfaces, as hierarchical structures or oleophobic designs.